Data_Sheet_2_Lithium Chloride Exerts Differential Effects on Dentinogenesis and Osteogenesis in Primary Pulp Cultures.pdf

Wnt/β-catenin signaling is known to play essential roles in odontoblast differentiation and reparative dentin formation. Various Wnt activators including LiCl have been increasingly studied for their effectiveness to induce repair of the dentin-pulp complex. LiCl is a simple salt thought to activate Wnt/β-catenin signaling by inhibiting GSK3β. Previous in vitro and in vivo studies showed that LiCl increased odontoblast differentiation and enhanced reparative dentin formation. However, the underlying molecular and cellular mechanisms by which LiCl regulates odontoblast and osteoblast differentiation during reparative dentinogenesis are not well-understood. Our in vitro studies show that exposure of early dental pulp progenitors to LiCl increased the survival and the pool of αSMA+ progenitors, leading to enhanced odontoblast and osteoblast differentiation. The positive effects of LiCl in the differentiation of osteoblasts and odontoblasts from αSMA+ progenitors are mediated by Wnt/β-catenin signaling. Our results also showed that continuous and late exposure of dental pulp cells to LiCl increased the expression of odontoblast markers through Wnt/β-catenin signaling, and the number of odontoblasts expressing DMP1-Cherry and DSPP-Cerulean transgenes. However, unlike the early treatment, both continuous and late treatments decreased the expression of Bsp and the expression of BSP-GFPtpz transgene. These observations suggest that prolonged treatment with LiCl in more mature cells of the dental pulp has an inhibitory effect on osteoblast differentiation. The inhibitory effects of LiCl on osteogenesis and Bsp were not mediated through Wnt/β-catenin signaling. These observations suggest that the effects of LiCl, and GSK3β antagonists on reparative dentinogenesis involve multiple pathways and are not specific to Wnt/β-catenin signaling.

已知Wnt/β-连环蛋白信号通路（Wnt/β-catenin signaling）在成牙本质细胞分化与修复性牙本质形成中发挥关键作用。目前，包括氯化锂（LiCl）在内的多种Wnt通路激活剂，在诱导牙本质-牙髓复合体修复的有效性方面受到了越来越多的研究关注。氯化锂作为一种简单盐类，被认为通过抑制糖原合成激酶3β（GSK3β）来激活Wnt/β-连环蛋白信号通路。
既往体外与体内研究均表明，氯化锂可促进成牙本质细胞分化，并增强修复性牙本质的形成。然而，在修复性牙本质生成过程中，氯化锂调控成牙本质细胞与成骨细胞分化的潜在分子及细胞机制，目前仍未得到充分阐明。
本团队的体外研究显示，早期牙髓祖细胞暴露于氯化锂环境后，其存活能力与α平滑肌肌动蛋白阳性（αSMA+）祖细胞的细胞池均得到扩增，进而促进成牙本质细胞与成骨细胞的分化。氯化锂对αSMA+祖细胞向成牙本质细胞、成骨细胞分化的正向调控作用，通过Wnt/β-连环蛋白信号通路介导。
研究结果同时表明，持续或晚期暴露于氯化锂的牙髓细胞，可通过Wnt/β-连环蛋白信号通路上调成牙本质细胞标志物的表达，同时增加表达DMP1-Cherry与DSPP-Cerulean转基因的成牙本质细胞数量。但与早期处理不同，持续与晚期氯化锂处理均会下调骨唾液蛋白（Bsp）的表达，以及BSP-GFPtpz转基因的表达水平。
上述观察结果提示，对牙髓组织中更成熟的细胞进行长期氯化锂处理，会对成骨细胞分化产生抑制作用。氯化锂对成骨过程及骨唾液蛋白表达的抑制效应，并非通过Wnt/β-连环蛋白信号通路介导。综上，氯化锂及糖原合成激酶3β拮抗剂在修复性牙本质生成中的调控作用涉及多条信号通路，并非仅特异性依赖Wnt/β-连环蛋白信号通路。